Ancient sea reptile remains rediscovered in museum collection after 75 years

Life reconstruction of a polycotylid plesiosaur.

Photograph: Joschua Knüppe

Forgotten bones of an ancient sea monster shed light on a poorly known timeframe from the Age of Dinosaurs in Europe.

Shortly before World War II, miners in what is now the city of Unna in western Germany, were excavating through overburden to reach rich coal deposits when they unexpectedly uncovered the remains of an extinct marine reptile that had lain undisturbed for over 92 million years. The fossils eventually found their way to the nearby Ruhr Museum in Essen, in North Rhine-Westphalia. There they stayed, and were almost forgotten for over 75 years until an international team of researchers rediscovered the bones and revealed their significance.

The fossils include a series of vertebrae from the neck of a plesiosaur - a type of sea reptile that resembled the popular image of the Loch Ness monster. Plesiosaurs dominated the oceans during the Age of Dinosaurs, and may have reached lengths of up to 15 metres.

"Plesiosaur fossils have been found on every continent, and in rocks that geologically range over some 140 million years, but they are still very rare for some ancient timeframes in some parts of the world" said Dr Benjamin Kear from the Museum of Evolution at Uppsala University, an author on the study.

"The plesiosaur remains from Unna come from one of these mysterious timeframes, known as the Turonian, and are important because they reveal new evidence of a fast swimming plesiosaur called a polycotylid that would have been about three metres long".

Polycotylids had long-snouted crocodile-like heads, and would have fed on fish and squid-like cephalopods. Their fossils are very rare in Europe, thus the Unna remains represent an important new global occurrence.

The new study also identifies the remains as being anatomically unusual, and potentially representing a new species that has only come to light because of significant museum collections.